Granulation of a Stevia sweetener

ABSTRACT

A method for making a granulated Stevia sweetener is described. The resulting sweetener has a desirably high solubility level.

RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No.16/017,643, filed Jun. 25, 2018, now U.S. Pat. No. 10,499,661, which isa continuation of U.S. application Ser. No. 13/509,552, filed Jul. 30,2012, now U.S. Pat. No. 10,004,245, which is a national stageapplication of International Application No. PCT/US2010/055960, filedNov. 9, 2010, which claims the benefit of priority of U.S. ProvisionalPatent Application No. 61/260,465, filed Nov. 12, 2009, U.S. ProvisionalPatent Application No. 61/260,593, filed Nov. 12, 2009, and U.S.Provisional Patent Application No. 61/290,778, filed Dec. 29, 2009, andwhich is a continuation-in-part of U.S. patent application Ser. No.12/720,888, filed Mar. 10, 2010, now U.S. Pat. No. 8,334,006, and U.S.patent application Ser. No. 12/753,470, filed Apr. 2, 2010, now U.S.Pat. No. 8,337,927 which applications are all hereby incorporated byreference in their entireties.

FIELD OF THE INVENTION

The invention relates to a process for the compaction and granulation ofindividual or combined sweet glycosides from a Stevia rebaudiana Bertoniplant extract, and more particularly for making a substantiallydust-free granulated sweetener which may contain Stevia sweeteners withor without other co-ingredients such as but not limited to caloric ornon-caloric sweeteners, taste modifiers and flavor modifiers.

DESCRIPTION OF THE RELATED ART

High intensity sweeteners possess a sweetness level many times exceedingthat of sucrose. They are used widely in manufacturing of diet andreduced calorie food and beverage products. Although a natural caloricsweetener such as sucrose, fructose, and glucose provide the mostdesirable taste to consumers, they are caloric and cause increases inblood glucose levels. High intensity sweeteners, on the other hand, areessentially non-caloric, do not affect blood glucose levels, and providelittle or no nutritive value.

However, high intensity sweeteners that generally are used as sugarsubstitutes possess taste characteristics which are different than thoseof sugar, such as sweet taste with different temporal profile, maximalresponse, flavor profile, mouthfeel, and/or adaptation behavior. Forexample, the sweet taste of some high intensity sweeteners is slower inonset and longer in duration than that of sugar, and thus change thetaste balance of a food composition. Because of these differences, theuse of high intensity sweeteners in replacing a bulk sweetener such assugar in a food or beverage product causes an imbalance in the temporaland/or flavor profile. If the taste profile of high intensity sweetenerscan be modified to impart desired taste characteristics that aresimilar, identical, or nearly identical to those of sugar or othernatural caloric sweeteners, they can provide low calorie beverages andfood products with taste characteristics that are more desirable toconsumers. To attain the sugar-like temporal and/or flavor profile,several ingredients have been suggested.

On the other hand, high intensity sweeteners may have some cost andfunctional advantages compared to sugar. The competition between sugarand non-sugar high intensity sweeteners is strong in, for example, thesoft drinks industry, especially in countries where their use andproduction is permitted and also in countries with overvalued sugarprices.

At present, high intensity sweeteners are used worldwide. They can be ofboth synthetic and natural origin.

Non-limiting examples of synthetic high intensity sweeteners includesucralose, potassium acesulfame, aspartame, alitame, saccharin,neohesperidin dihydrochalcone synthetic derivatives, cyclamate, neotame,dulcin, suosan,N-[N-[3-(3-hydroxy-4-methoxyphenyl)propyl]-L-α-aspartyl]-L-phenylalanine1-methyl ester,N-[N-[3-(3-hydroxy-4-methoxyphenyl)-3-methylbutyl]-L-α-aspartyl]-L-phenylalanine1-methyl ester,N-[N-[3-(3-methoxy-4-hydroxyphenyl)propyl]-L-α-aspartyl]-L-phenylalanine1-methyl ester, salts thereof, and the like.

Non-limiting examples of natural high intensity sweeteners includeStevioside, Rebaudioside A, Rebaudioside B, Rebaudioside C, RebaudiosideE, Rebaudioside F, Steviolbioside, Dulcoside A, Rubusoside, mogrosides,brazzein, neohesperidin dihydrochalcone (NHDC), glycyrrhizic acid andits salts, thaumatin, perillartine, pernandulcin, mukuroziosides,baiyunoside, phlomisoside-I, dimethyl-hexahydrofluorene-dicarboxylicacid, abrusosides, periandrin, carnosiflosides, cyclocarioside,pterocaryosides, polypodoside A, brazilin, hernandulcin, phillodulcin,glycyphyllin, phlorizin, trilobatin, dihydroflavonol,dihydroquercetin-3-acetate, neoastilibin, trans-cinnamaldehyde, monatinand its salts, selligueain A, hematoxylin, monellin, osladin,pterocaryoside A, pterocaryoside B, mabinlin, pentadin, miraculin,curculin, neoculin, chlorogenic acid, cynarin, siamenoside and others.

High intensity sweeteners can be derived from the modification ofnatural high intensity sweeteners, for example, by fermentation,enzymatic treatment, or derivatization.

At present about eleven high intensity sweeteners are used worldwide.These are acesulfame-K, alitame, aspartame, cyclamate, glycyrrhizin,NHDC, saccharin, Stevioside, sucralose, thaumatin, neotame, andRebaudioside A.

The high intensity sweeteners can be grouped into three generations. Thefirst generation is represented by cyclamate, glycyrrhizin andsaccharin, and has a long history of use in food. The second generationincludes acesulfame-K, aspartame, NHDC and thaumatin. Alitame, neotame,sucralose, Stevioside, and Rebaudioside A belong to the thirdgeneration.

The standard sweetening power associated with each high intensitysweetener is given in TABLE 1. However, when they are used in blends,the sweetening power can change significantly.

TABLE 1 Sweetness Power of High Intensity Sweeteners Sweetener Sweetnesspower Saccharose 1 Acesulfame-K 200 Alitame 2000 Aspartame 200 Cyclamate30 Glycyrrhizin 50 NHDC 1000 Saccharine 300 Stevioside 200 RebaudiosideA 450 Thaumatin 3000 Sucralose 600

On the other hand, ‘natural’ and ‘organic’ foods and beverages havebecome the “hottest area” in the food industry. The combination ofconsumers' desire, advances in food technology, and new studies linkingdiet to disease and disease prevention have created an unprecedentedopportunity to address public health through diet and lifestyle.

A growing number of consumers perceive the ability to control theirhealth by enhancing their current health and/or hedging against futurediseases. This creates a demand for food products with enhancedcharacteristics and associated health benefits, specifically a food andconsumer market trend towards “whole health solutions” lifestyle. Theterm “natural” is highly emotive in the world of sweeteners and has beenidentified as one of key trust, along with “whole grains”,“heart-healthy” and “low-sodium”. ‘Natural’ term is closely related to‘healthier’.

In this respect, natural high intensity sweeteners can have a bettercommercial potential.

Stevia rebaudiana Bertoni is a perennial shrub of the Asteraceae(Cornpositae) family native to certain regions of South America. Theleaves of the plant contain from 10 to 20% of diterpene glycosides,which are around 150 to 450 times sweeter than sugar. The leaves havebeen traditionally used for hundreds of years in Paraguay and Brazil tosweeten local teas and medicines.

At present there are more than 230 Stevia species with significantsweetening properties. The plant has been successfully grown under awide range of conditions from its native subtropics to the cold northernlatitudes.

Steviol glycosides have zero calories and can be used wherever sugar isused. They are ideal for diabetic and low calorie diets. In addition,the sweet steviol glycosides possess functional and sensory propertiessuperior to those of many other high intensity sweeteners.

The extract of Stevia rebaudiana plant contains a mixture of differentsweet diterpene glycosides, which have a single base—steviol—and differby the presence of carbohydrate residues at positions C13 and C19. Theseglycosides accumulate in Stevia leaves and compose approximately 10%-20%of the total dry weight. Typically, on a dry weight basis, the fourmajor glycosides found in the leaves of Stevia are Dulcoside A (0.3%),Rebaudioside C (0.6%), Rebaudioside A (3.8%) and Stevioside (9.1%).Other glycosides identified in Stevia extract include Rebaudioside B, C,D, E, and F, Steviolbioside and Rubusoside. Among steviol glycosides,only Stevioside and Rebaudioside A are available on a commercial scale.

The physical and sensory properties are well studied only for Steviosideand Rebaudioside A. The sweetness potency of Stevioside is around 210times higher than sucrose, Rebaudioside A is between about 200 and about400 times higher than sucrose, and Rebaudioside C and Dulcoside A areeach around 30 times higher than sucrose. Rebaudioside A is consideredto have most favorable sensory attributes of the four major steviolglycosides (TABLE 2).

TABLE 2 Physical and Sensory Properties of Steviol Glycosides Opticalrotation [α]²⁵ _(D) T_(melt), Mol. (H₂O, 1%, Solubility Relative Qualityof Name Formula ° C. Weight w/v) in water, % sweetness taste SteviolC₂₀H₃₀O₃ 212-213 318.45 ND ND ND Very bitter Steviolmonoside C₂₆H₄₀O₈ ND480.58 ND ND ND ND Stevioside C₃₈H₆₀O₁₈ 196-198 804.88 −39.3 0.13 210Bitter Rebaudioside A C₄₄H₇₀O₂₃ 242-244 967.01 −20.8 0.80 200-400 LessBitter Rebaudioside B C₃₈H₆₀O₁₈ 193-195 804.88 −45.4 0.10 150 BitterRebaudioside C C₄₄H₇₀O₂₂ 215-217 951.01 −29.9 0.21 30 BitterRebaudioside D C₅₀H₈₀O₂₈ 248-249 1129.15 −29.5 1.00 220 Like (ethanol)sucrose Rebaudioside E C₄₄H₇₀O₂₃ 205-207 967.01 −34.2 1.70 170 Likesucrose Rebaudioside F C₄₃F₆₈O₂₂ ND 936.99 −25.5 ND (methanol) DulcosideA C₃₈H₆₀O₁₇ 193-195 788.87 −50.2 0.58 30 Very bitter SteviolbiosideC₃₂H₅₀O₁₃ 188-192 642.73 −34.5 0.03 90 Unpleasant Rubusoside C₃₂H₅₀O₁₃ND 642.73 642.73 ND 110 Very bitter

There are several publications on the purification of some individualsteviol glycosides.

Several patents describe the general process that can be used to make aStevia extract: U.S. Pat. Nos. 3,723,410; 4,082,858; 4,171,430;4,361,697; 4,599,403; 4,892,938; 5,112,610; 5,962,678; 5,972,120;6,031,157; 6,080,561; 7,807,206; and JP No. 01-131191; each of which isincorporated by reference in their entirety herein.

Generally, the production of a Stevia extract includes extraction ofplant material with water or water-organic solvent mixture,precipitation of high molecular weight substances, deionization, anddecolorization, purification on specific macroporous polymericadsorbents, concentration and drying.

The glycosides from leaves can be extracted using either water ororganic solvent extraction. Supercritical fluid extraction and steamdistillation have been described as well. Methods for recovery ofditerpene sweet glycosides from Stevia rebaudiana using membranetechnology, and water or organic solvents, such as methanol and ethanol,also are described in the literature.

The Stevia extract is dried by spray drying and/or vacuum dryingtechnology to evaporate moisture and processing solvents from theextract. The resulting powder contains very fine particles with a verylow moisture content and low bulk density, which makes it very dusty tohandle during food application processing.

To overcome the issues associated with the very fine particle size anddust, agglomeration technology is used to reduce the hazardous nature ofdust particles and their associated handling difficulty. However mostcommercial or industrial agglomeration technology requires the use of abinder, which may be water or a solution of adhesive molecules.

Using wet agglomeration technology, in which a wet binding component isutilized, may adversely affect the physical and chemical characteristicsof Stevia molecules, especially the solubility of the Stevia extract.The current invention is able to provide a physical form of a Steviasweetener product which is much more user-friendly and reduces dust orfines, without substantially changing the physical and chemicalcharacteristics of the different Stevia sweetener molecules.

To enhance the sweetness profile and to reduce the aftertaste of highintensity sweeteners, one or more co-ingredients can be combined forspecific food and beverage applications. This invention also helps indelivering the high intensity sweetener and one or more co-ingredientstogether in a calibrated proportion in a granulated particle form, whichis process- and user-friendly.

Due to the physicochemical properties of Stevia sweeteners, not allgranulation or agglomeration techniques are suitable to producecompositions with the desired properties. In particular, it is wellknown that Rebaudioside A exhibits so called polymorphism (Zell et al.,“Investigation of Polymorphism in Aspartame and Neotame UsingSolid-State NMR Spectroscopy.” Tetrahedron 56(6603-6616), 2000).Rebaudioside A amorphous, anhydrous and solvate forms differsignificantly from each other in terms of solubility which is one of themain criteria for the commercial viability of a sweetener. In thisregard, as shown in Table 3, the hydrate form of Rebaudioside A displaysthe lowest solubility (Prakash et al., “Development of rebiana, anatural, non-caloric sweetener.” Food Chem. Toxicol. 46(S75-S82), 2008).It was shown that Rebaudioside A may transform from one polymorph formto another at certain conditions (U.S. patent application Ser. No.11/556,049) as summarized in Table 3. Therefore, processes employed inRebaudioside A manufacturing should minimize the formation of forms withundesired characteristics. Many agglomeration techniques which allowcontact of a solvent with a Rebaudioside A may facilitate formation ofsolvate forms with undesired characteristics. In case of water or awater-containing mixture or solution coming into contact withRebaudioside A, a hydrate form may be obtained which is characterized asthe form with lowest solubility.

TABLE 3 Properties of Rebaudioside A forms (U.S. patent application No.11/556,049) Polymorph Forms Form 1 Form 2 Form 3 Form 4 HydrateAnhydrous Solvate Amorphous Rate of Very low Intermediate High Highdissolution in (<0.2% in (<30% in 5 (>30% in (>35% in H₂O at 25° C. 60minutes) minutes) 5 minutes) 5 minutes) Alcohol content <0.5% <1% 1-3%<0.05% Moisture content   >5% <1%  <3% 6.74%

In addition, many processes employ binding agents or other auxiliarycompounds which appear in the final product, thereby undesirablyreducing the principal ingredient content.

There is therefore a significant need for a process of manufacturinggranulated or agglomerated Rebaudioside A or other steviol glycosideshaving a desirably high solubility and containing a significant ormaximized amount or concentration of the principal compound.

U.S. patent application Ser. No. 10/108,561 describes a method ofproducing corn starch granulate by combining the starch with granulationfluid, subjecting the mixture to wet sieving, drying and sizing. It isnoted that the addition of granulation fluids in the case of Steviasweeteners and Rebaudioside A will facilitate formation of lowsolubility polymorphs, which in turn will reduce the overall solubilityof the final composition.

U.S. patent application Ser. No. 11/873,610 provides a method ofproducing granulated sweetening composition comprising poorly solublepolyol and hydrogenated dextrin. It is noted that including auxiliarycompounds in a composition reduces the content of active ingredient.

U.S. patent application Ser. No. 11/979,530 describes a method forproducing granules from powder by subjecting it to compacting force toproduce a compacted mass comprising a mixture of fine particles andgranules and separating the fine particles from granules by entrappingthe fine particles in a gas stream.

U.S. Pat. No. 6,706,304 describes a method of preparing granularsweetener comprising Aspartame and Acesulfame K as active ingredients.The mixture of the ingredients was fed to the roller-compactor typegranulator to obtain a granulated sweetener composition. It is notedthat due to polymorphism of Stevia sweeteners and rebaudioside A, lowsolubility forms may be formed during such a process which will resultin a final composition with an undesirably low solubility.

SUMMARY OF THE INVENTION

The invention is directed to a method for producing a sweetenercomprising the steps of providing a Stevia sweetener powder, reducingthe particle size of the Stevia sweetener powder, treating the Steviasweetener powder under reduced pressure and elevated temperature,cooling down the treated Stevia sweetener powder; and holding the highsolubility Stevia sweetener powder at low temperature to obtain a highsolubility Stevia sweetener powder with increased solubility.

Hereinafter, unless specified otherwise, the solubility of a material isdetermined in reverse osmosis water at room temperature. Where thesolubility is expressed as “%” it to be understood as number of grams ofmaterial soluble in 100 grams of solvent.

The invention is also directed to a method of roll compaction of asweetener, starting with a high solubility sweetener powder, andintroducing the high solubility sweetener powder to a roller compactionapparatus to produce a compacted material, introducing the compactedmaterial to a size reducing apparatus to obtain a granule mixture, andfractioning the granule mixture through sieves of various sizes toobtain a granulated Stevia sweetener.

The invention further includes a high solubility Stevia sweetenerpowder, and a granulated Stevia sweetener.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the invention. The drawings illustrate embodiments ofthe invention and together with the description serve to explain theprinciples of the embodiments of the invention.

FIG. 1 shows the particle size distribution of a high solubilityRebaudioside A powder made in accordance with one embodiment of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

A process for the granulation of a Stevia sweetener, particularlyRebaudioside A, is described herein. The process includes the steps ofreducing the particle size of a Rebaudioside A composition, drying theRebaudioside A particles using a thermal treatment process, holding theRebaudioside A particles under nitrogen gas, compacting the particles,then granulating them to a desired mesh size. The resulting granulatedRebaudioside A composition exhibits superior solubility and handlingperformance as compared to other Rebaudioside A compositions. Althoughthe following description describes Rebaudioside A, it is to beunderstood that the processes and methods described herein are alsosuitable for use with any type of Stevia sweetener.

Crystalline Rebaudioside A has an inherently very low solubility,ranging from about 1%-2%. As described above, Rebaudioside A exhibitspolymorphism, resulting in a variety of forms with very differentcharacteristics and handling properties. The hydrate form has very lowsolubility (less than 0.2%), and is therefore not commercially viable asa sweetener. The solvate form has a solubility typically greater than30%, but this form has only of scientific interest and cannot be usedfor food or beverage applications because the level of residual alcohol(1-3%) makes it unfit for use in foods and beverages. The anhydrous formhas a solubility reported in literature of a maximum of up to about 30%solubility. The amorphous form has as solubility generally greater than35%, but in the refining process, the amorphous form has to be dissolvedin water and spray dried. The spray drying process necessitates the useof very diluted solutions, and spray drying itself is a very high energyconsuming process, so this is not a viable option for the commercialproduction of Rebaudioside A.

The need exists, therefore, for a process in which a high solubilityRebaudioside A is obtained by a process which does not requiresignificant dilution or a high energy level, and which does not resultin a product having unacceptably high levels of alcohol. The process ofthe present invention achieves these objectives by creating a form ofRebaudioside A with a high level of solubility, but without theconcomitant dilution, cost, or high alcohol content associated withother processes.

In one embodiment of the present invention, an initial material,comprising sweet glycosides of the Stevia rebaudiana Bertoni plantextract, which includes Stevioside, Rebaudioside A, Rebaudioside B,Rebaudioside C, Rebaudioside E, Rebaudioside F, Steviolbioside,Dulcoside A, Rubusoside and/or a mixture thereof was subjected toparticle size reduction to produce a powder with mean particle size ofbetween about 20-60 μm, preferably between about 25-40 μm. The powderwith a particle size of less 20 μm exhibits low flowability reducing theefficiency of the process, whereas particles larger than 60 μm yield aproduct with low solubility. Any apparatus which may reduce a particlesize of a solid substance, such as rotary mill, ball mill, pulverizeretc may be used for this process.

The powder thus obtained is subjected to a thermal treatment processunder vacuum at between about 0-100 mbar pressure, preferably betweenabout 5-15 mbar pressure. The duration of the thermal treatment may bebetween about 1-24 hours, preferably between about 2-6 hours. Thetemperature of the thermal treatment is between about 90-130° C.,preferably between about 100-110° C. The powder is subjected to thethermal treatment for a period of time and at a temperature sufficientto remove all the water from the material, without significant productdegradation.

Upon completion of the thermal treatment, preheated nitrogen isintroduced into the vacuum chamber to equalize the pressure in thechamber with ambient pressure. The temperature of the preheated nitrogenin this nitrogen holding step is about 5° C. lower than the thermaltreatment temperature. The vacuum chamber is connected to a vent whichprevents excessive pressure buildup. The nitrogen flow is maintained atvelocity which equals 1/10 of the vacuum chamber volume per minute. Thenitrogen temperature is gradually decreased to about 25° C. over aperiod of between about 3-12 hours, preferably between about 4-6 hours.The nitrogen holding conditions are selected to provide uniform andsmooth cooling conditions. Although nitrogen is described, any othersubstantially inert gas which will not hydrate, oxidize or otherwisechemically affect the product may be used.

In one embodiment, the high solubility powder was held under nitrogen ata temperature of between about 10-50° C., preferably between about10-30° C. A temperature lower than 10° C. was found to result in ambientmoisture condensation on the product further in the process, resultingin the low solubility hydrated form of Rebaudioside A. If the powder wastreated with a temperature higher than 50° C., it resulted in anoverheated compacted mass during roll compaction which quickly cooleddown to the ambient temperature after compaction and yielded aRebaudioside A product with low solubility.

The purpose of this process is to obtain a polymorph form ofRebaudioside A with a high solubility. The high solubility RebaudiosideA powder obtained by this process has a solubility that is greater thanabout 30%, or preferably is at least about 35% or at least about 40%.

As discussed above, the conventionally prepared anhydrous form ofRebaudioside A demonstrates a solubility of up to about 30%, and theamorphous form demonstrates a solubility that can be greater than 35%,but must be diluted significantly and spray dried when it is refined.Prior to the present invention, it has not been possible to provide ahigh solubility form of Rebaudioside A that is stable, easy to refine ona large scale, and does not require spray drying or other dilutingprocesses during a commercial refining process. It was unexpectedlydiscovered that using the process of the present invention, includingthermally treating a Rebaudioside A powder under vacuum and holding thepowder under nitrogen gas, followed by dry roll compaction andgranulation, a stable but very highly soluble form of Rebaudioside A canbe produced.

While not intending to be bound by theory, it is believed that the highsolubility form of Rebaudioside A made by the present invention is ananhydrous form of Rebaudioside A having significantly improvedsolubility properties as compared to a conventional anhydrous form ofRebaudioside A, and which can be refined into a granular form withoutthe dilution or spray drying required to refine the amorphous form ofRebaudioside A.

Granulation refines the high solubility Rebaudioside A powder into aform suitable for further handling and for industrial or consumer use.Dry granulation provides numerous advantages over wet agglomeration,such as being a continuous process capable of internally recyclingoff-specification granules, not requiring any additional bindingmaterials, and not requiring an additional drying step once the productis granulated.

One method of granulation is by using roll compaction, in which thepowder is fed to two counter-rotating rolls which draw the powderbetween the rolls due to friction and compact the powder into a sheet orlayer of material. Roll compaction inherently reduces the solubility ofmaterials. Therefore, to achieve a desirable level of solubility in agranulated product, it is desirable to have a starting material with ahigh solubility rate prior to compaction, so that the resultingcompacted and granulated material has the greatest solubility possiblefor a given material.

The granulated material made in accordance with the present inventionadvantageously yields a product with favorable characteristics such assolubility, particle size distribution and purity. In fact, it wasdiscovered that the dissolution rate of the high solubility RebaudiosideA granulated particles of the present invention is actually greater, andeven significantly greater, than the dissolution rate of the highsolubility Rebaudioside A powder prior to roll compaction. While notintending to be bound by theory, it is believed that the granulationprocess of the present invention improves the dispersibility of the highsolubility Rebaudioside A, resulting in a faster dissolution rate.

During compaction, if the roll pressure is too low, it may result in theformation of “loose” granules with poor mechanical stability. If theroll pressure is too high, it may result in “over-compacted” materialwhich has a slower dissolution rate. In one embodiment of the presentinvention, the roll speed was between about 5-20 rpm, preferably betweenabout 7-10 rpm, and more preferably about 9 rpm. The roll pressure wasbetween about 10-60 bar, preferably between about 30-50 bar, and morepreferably about 45 bar.

Numerous factors affect the solubility of a dry material, including thedensity of the material. It was found that suitable density values whichprovided the desired solubility values range from between about 0.35 toabout 0.45 g/cc after roll compaction.

The compacted Rebaudioside A material can then processed by agranulating apparatus. In one embodiment, the apparatus contained twogranulators—a pre-granulator and a fine granulator. The purpose of thegranulators is to generate granules from compacted material produced bythe roll compactor. Each granulator is equipped with rotors which pressthe coarse material through a U-shaped screen. If the screen size is toosmall, it results in an excessive amount of fine particles. If thescreen size is too large, it produces large particles with a lowerdissolution rate.

In one embodiment, the rotors were rotating at a rate of between about50-2000 rpm, preferably between about 100-200 rpm, and more preferablyat about 150 rpm. The granulators were equipped with screens which sizeswere between about 0.5-6.0 mm, preferably between about 1-4 mm, and morepreferably about 3.1 mm for the pre-granulator and about 1.6 mm for thefine granulator.

The resulting granulated Rebaudioside A product from this embodiment wasfractioned on the sieves of US Mesh ##8; 10; 14; 20; 40 and 60. Theresults are presented in Table 4.

TABLE 4 Particle size distribution US Mesh # % retained 8 0 10 0.1 1426.3 20 39.5 40 24.8 60 6.5

About 2.8% of the material passed through the US Mesh #60 sieve.

The granulated Rebaudioside A sweetener obtained through the method ofthe present invention has a solubility ranging from about 1.0% togreater than 40%.

In one embodiment of the invention, the high solubility Rebaudiosde Apowder can be mixed with other ingredients to form a Rebaudioside Ablend prior to granulation. The high solubility Rebaudioside A powder iscapable of being blended with other ingredients to achieve the properdistribution of all ingredients in the final product. Non-limitingexamples of other ingredients which may be combined with the highsolubility Rebaudioside A powder prior to granulation include: naturaland synthetic high intensity sweeteners as described previously; naturalsweeteners such as sucrose, fructose, glucose, maltose, lactose,tagatose, and palatinose; sugar alcohols such as erythritol; flavormodifying agents such as spices and extracts; taste modifying agentssuch as thaumatin, glycyrrhizin, Rebaudioside C, and Rebaudioside D;bulking agents or mouthfeel modifiers such as Fibersol®, soluble cornfiber, gum Arabic, pectin, isomaltooligosaccharide; and combinationsthereof.

It has been discovered that by balancing the use of other ingredients incombination with Rebaudioside A, the flavor and temporal profiles of theresulting sweetener can be improved. For example, while not intending tobe bound by theory, it is believed that using a very small amount of ataste modifying agent may serve to saturate or block the specific tastebuds during the early part of consumption, thus making those taste budsunavailable for the transmittal of specific taste signals to the brainduring the consumption of the rest of the beverage or food. The tastemodifying agent itself may have a very high degree of the particulartaste, such as bitterness, which is to be blocked by saturating thereceptors on the tongue with that taste.

The sweetness profile of Rebaudioside A may also be enhanced with theuse of sugar, such as cane or beet sugar. Although sugar and Steviasweeteners have different melting characteristics and solubility, it isbelieved that the use of the dry roll compaction granulation process ofthe present invention results in a reduced calorie sugar-containingsweetener composition which is uniform and provides a consistentdispersion when used in a food or beverage application.

The following examples illustrate various embodiments of the invention.It will be understood that the invention is not limited to thematerials, proportions, conditions and procedures set forth in theexamples, which are only illustrative.

EXAMPLE 1 Preparation of High Solubility Rebaudioside A

100 kg of Rebaudioside A, containing Stevioside 0.2%, Rebaudioside C0.2%, Rebaudioside F 0.3%, Rebaudioside A 97.5%, Rebaudioside D 1.1%,Rebaudioside B 0.5%, all percentages being on a percent dry weightbasis, and having water solubility of 1.6% was placed into rotary blademilling machine and pulverized for 20 minutes. The resulting powder wasanalyzed by Beckman Coulter LS 13 320 Laser Diffraction Particle SizeAnalyzer. The results are summarized in Table 5.

TABLE 5 Powder Laser Diffraction Analysis Results Volume StatisticsOperation Mode Calculations: from 0.375 μm to 2000 μm Mean: 31.07 μmMedian: 23.11 μm Mean/Median ratio: 1.344 Mode: 50.22 μm S.D.: 27.15 μmVariance: 737.4 μm² C.V.: 87.4% Distribution <10% 3.356 μm <25% 10.11 μm<50% 23.11 μm <75% 45.76 μm <90% 70.19 μm

The obtained powder was loaded into a 1000 L rotary vacuum dryer anddried at 105° C. at 10 mbar pressure for 3 hours. After 3 hours,preheated nitrogen at 100° C. was introduced into the vacuum chambertill ambient pressure was reached. Upon reaching ambient pressure, thevacuum dryer was connected to a vent and the nitrogen flow was continuedat 100 L/min for a 4-hour time period. The temperature of the nitrogengas was gradually decreased by 5° C. decrements until reaching 25° C.during the course of the 4-hour time period. A sample of the powder waswithdrawn from the dryer and the solubility tested in deionized water atroom temperature. The solubility was 41.1%, and the dissolution time was7 minutes. The particle size distribution of the high solubilityRebaudioside A powder is shown in FIG. 1.

EXAMPLE 2 Granulation of Rebaudioside A

50 kg of high solubility Rebaudioside A prepared according to EXAMPLE 1was placed into a 500 L double cone powder mixer and nitrogen at 10° C.was fed to the vessel for 1 hour. The powder was transferred toAlexanderwerk WP 50N/75 roller compactor. The compactor was operating at9 rpm and 45 bar pressure. The compacted mass was fed to apre-granulator and a fine granulator with rotors at rotating at 150 rpm.The screen size for the pre-granulator was 3.1 mm and for the finegranulator was 1.6 mm. The “overs” (particles that are too large) and“fines” (particles that are too small) were separated by top screenhaving a screen size of US Mesh 10 and bottom screen of US Mesh 40. The% ratio of “overs”:“product”:“fines” was 0.3%:72.1%:27.6% respectively.

EXAMPLE 3 Granulation of Rebaudioside A

50 kg of high solubility Rebaudioside A prepared according to EXAMPLE 1were granulated according to procedure of EXAMPLE 2. The compactor wasoperating at 18 rpm and 65 bar pressure. The compacted mass was fed to apre-granulator and a fine granulator with rotors at rotating at 300 rpm.The screen size for the pre-granulator was 5 mm and for the finegranulator was 3 mm.

EXAMPLE 4 Granulation of Rebaudioside A

50 kg of high solubility Rebaudioside A prepared according to EXAMPLE 1was granulated according to procedure of EXAMPLE 2. The compactor wasoperating at 9 rpm and 45 bar pressure. The compacted mass was fed topre-granulator and fine granulators with rotors at rotating at 150 rpm.The screen size for the pre-granulator was 2 mm and for the finegranulator was 0.5 mm. The “overs” and “fines” were separated by topscreen of US Mesh #10 and bottom screen of US Mesh #40. The yield ofproduct was 34%, whereas 66% of product passed through US Mesh #40.Subsequent sifting of the material that passed through the US Mesh #40through a US Mesh #80 sieve resulted in 28% of powder passing throughthe US Mesh #80.

EXAMPLE 5 Dissolution Rate of High Solubility Rebaudioside A

Four batches of high solubility Rebaudioside A powder were used forpreparing the granulated product by using the roll compaction technologyas described above. All powder and granulated samples were tested fortheir solubility and dispersion time. Testing was conducted by adding5.0 g of powder or granulated high solubility Rebaudioside A in 500 mlwater at ambient temperature. The mixture was then agitated with amagnetic stirrer to create a significant vortex for proper mixing. Thedissolution rate was timed on a stop watch starting as soon as the highsolubility Rebaudioside A was added directly to agitated water. Thedata, summarized in Table 6, showed that granulation shortened thedissolution time (the time to have clear solution) without any loss ofsolubility.

TABLE 6 Dissolution Times and Rates of High Solubility Rebaudioside APowder and Granular Form % Rate Dissolu- Dissolu- Dissolu- Dissolu-Increase tion Time tion Rate tion Time tion Rate from Batch (Powder)(Powder (Granular) (Granular) Powder 1 7 min 11 sec 0.70 g/min 6 min 35sec 0.76 g/min  8.6% 2 10 min 5 sec  0.50 g/min 4 min 41 sec 1.07 g/min114% 3 8 min 35 sec 0.58 g/min 5 min 36 sec 0.90 g/min  55% 4 13 min 12sec  0.38 g/min 5 min 11 sec 1.00 g/min 163%

The process of the present invention resulted in a unique Rebaudioside Apolymorph which demonstrated an unexpectedly higher degree of solubilityin water than other polymorphic forms. Although the foregoingembodiments describe the use of Rebaudioside A, it is to be understoodthat any Stevia-based sweetener may be used and prepared in accordancewith this invention, and all Stevia-based sweeteners are contemplated tobe within the scope of the present invention.

EXAMPLE 6 Additional Particle Size Distributions

An initial material, comprising sweet glycosides of the Steviarebaudiana plant extract, which includes one or more of Stevioside,Rebaudioside A, Rebaudioside B, Rebaudioside C, Rebaudioside D,Rebaudioside E, Rebaudioside F, Rebaudioside M, Rebaudioside N,Rebaudioside O, Steviolbioside, Dulcoside A, Rubusoside, other minorglycosides found in Stevia rebaudiana plants, and/or a mixture thereof,was subjected to particle size reduction to produce a powder with meanparticle size of less than about 260 μm. The powder had a solubility inwater at ambient temperature (between about 65-75° F. or about 18-24°C.) of at least about 1 g per 100 g of water, at least about 5 g per 100g of water, at least about 10 g per 100 g of water, at least about 15 gper 100 g of water, at least about 20 g per 100 g of water, at leastabout 25 g per 100 g of water, or at least about 30 g per 100 g ofwater. The powder was then granulated using the roll compaction methodas described above. Additional particle size distributions of thegranulated product were obtained.

The particle sizes obtained generally ranged from about 140 μm to about680 μm, more specifically from about 180 μm to about 600 μm, from about180 μm to about 420 μm, from about 150 μm to about 420 μm, or from about150 μm to about 260 μm. Each of the granulated samples had a greaterdissolution rate than its corresponding powder form. Tables 7a-e showparticle size distributions based on US Mesh sieve sizes as indicated inthe Tables. Microns (μm) listed in the tables are approximate sieve sizeopenings.

TABLE 7a Particle Size Distribution % Retained on Sieve Sample A # 30(600 μm) >14% # 60 (260 μm) >90% # 80 (180 μm) >99% Pass thru # 80  <1%

For Sample A, greater than about 90% of the granulated products had aparticle size greater than 260 μm.

TABLE 7b Particle Size Distribution % Retained on Sieve Sample B # 40(420 μm)  <5% # 60 (260 μm) <60% # 100 (150 μm) >95% Pass thru # 100 <5%

For Sample B, greater than about 95% of the granulated products had aparticle size greater than 150 μm and less than about 60% of the samplehad a particle size greater than 260 μm.

TABLE 7c Particle Size Distribution % Retained on Sieve Sample C # 40(420 μm) <65-80%   # 60 (260 μm) >95% # 80 (180 μm) >99% Pass thru #80 <1%

For Sample C, greater than about 95%, of the granulated products had aparticle size greater than about 260 μm based on the sieve openingsizes. Less than between about 65% to 80% had a particle size greaterthan 420 μm.

TABLE 7d Particle Size Distribution % Retained on Sieve Sample D # 40(420 μm)  ≤1% # 60 (260 μm) ≤15% # 100 (150 μm) ≤95% Pass thru # 100 ≤5%

For Sample D, less than or about 95% of the granulated products had aparticle size larger than 150 μm based on the sieve opening sizes.

TABLE 7e Particle Size Distribution Sample E # 16 (1200 μm)  <1% # 30(600 μm) <14% # 60 (260 μm) <90% # 80 (180 μm) >99% Pass thru # 100 (150μm)  <1%

For Sample E, greater than about 99% of the granulated products had aparticle size larger than 180 μm, and less than about 90% of thegranulated products had a particle size larger than about 260 μm, basedon the sieve opening sizes.

EXAMPLE 7 Dissolution Rates

Dissolution rates for selected samples of Rebaudioside A were evaluated.The samples were either in powder form having a particle size of lessthan about 260 μm, or in granular (granulated) form having the granularparticle size distributions described in Example 6 corresponding to theSample identification listed below. Dissolution rates were determinedusing the methodology of Example 5, and the results are provided inTable 8.

TABLE 8 Dissolution Times and Rates of Rebaudioside A Powder andGranular Form % Rate Dissolu- Dissolu- Dissolu- Dissolu- Increase Sampletion Time tion Rate tion Time tion Rate from ID (Powder) (Powder)(Granular) (Granular) Powder A 3 min 00 sec 1.67 g/min 2 min 32 sec 1.97g/min 18.42 B 3 min 02 sec 1.65 g/min 48 sec 6.25 g/min 279.17 D 3 min00 sec 1.67 g/min 50 sec 6.00 g/min 260.00 E 3 min 01 sec 1.66 g/min 2min 52 sec 1.74 g/min 5.23

The percent increase in dissolution rate of the granular product ascompared to the powder form ranges from about 5% to about 280%. Incertain embodiments, the percent increase in dissolution rate of asteviol glycoside composition as a granular product as compared to itspowder form at an ambient temperature is at least about 10%, 20%, 50%,100%, 150%, 200% or 250%.

Although the invention and its advantages have been described in detail,it should be understood that various changes, substitutions andalterations can be made herein without departing from the spirit andscope of the invention as defined by the appended claims. Moreover, thescope of the application is not intended to be limited to the particularembodiments of the invention described in the specification. As one ofordinary skill in the art will readily appreciate from the disclosure ofthe invention, the compositions, processes, methods, and steps,presently existing or later to be developed that perform substantiallythe same function or achieve substantially the same result as thecorresponding embodiments described herein may be utilized according tothe invention.

We claim:
 1. A method for producing a sweetener comprising the steps of:A) providing a Stevia sweetener powder; B) reducing the particle size ofthe Stevia sweetener powder to a particle size of less than 260 μm; C)treating the Stevia sweetener powder under reduced pressure of betweenabout 0 mbar to 100 mbar and an elevated temperature of between about90-130° C.; D) cooling down the treated Stevia sweetener powder to a lowtemperature of about 25° C.; and E) holding the cooled Stevia sweetenerpowder at the low temperature to obtain a high solubility Steviasweetener powder with an increased solubility of at least about 1 g per100 g of water at ambient temperature; and F) introducing the highsolubility Stevia sweetener powder to a roll compaction apparatus toproduce a compacted material; introducing the compacted material to asize reducing apparatus to obtain a granule mixture; and fractionatingthe granule mixture to obtain a granulated Stevia sweetener having aparticle size ranging from about 140 μm to about 680 μm and having adissolution rate greater than a dissolution rate of the high solubilityStevia powder.
 2. The method of claim 1, wherein the dissolution rate ofthe granulated Stevia sweetener is at least about 0.75 grams per minute.3. The method of claim 1 wherein Stevia sweetener is selected from agroup consisting of Stevioside, Rebaudioside A, Rebaudioside B,Rebaudioside C, Rebaudioside D, Rebaudioside E, Rebaudioside F,Rebaudioside M, Rebaudioside N, Rebaudioside O, Steviolbioside,Dulcoside A, Rubusoside, other minor glycosides found in Steviarebaudiana plants, and a mixture thereof.
 4. The method of claim 1,wherein cooling the treated Stevia powder comprises introducingpreheated nitrogen gas into a vacuum chamber and gradually reducing thenitrogen gas temperature.
 5. The method of claim 1, wherein the rollcompaction apparatus operates at between about 5 rpm and about 20 rpm,and at a roll pressure of between about 10 bar to about 60 bar toproduce the compacted material; and the size reducing apparatuscomprises a set of sequentially located granulators equipped with rotorsrotating at between about 50 rpm to about 2000 rpm to obtain the granulemixture.
 6. The method of claim 1 wherein the Stevia sweetener powder isselected from a group consisting of: Stevioside, Rebaudioside A,Rebaudioside B, Rebaudioside C, Rebaudioside D, Rebaudioside E,Rebaudioside F, Rebaudioside M, Rebaudioside N, Rebaudioside O,Steviolbioside, Dulcoside A, Rubusoside, other minor glycosides found inStevia rebaudiana plants, and a mixture thereof.
 7. The method of claim1, further comprising the step of combining the Stevia sweetener powderwith an additional ingredient before introducing the powder to the rollcompaction apparatus.
 8. The method of claim 1, wherein the additionalingredient is selected from the group consisting of: a high intensitysweetener; a natural sweetener; a sugar alcohol; a flavoring agent; aflavor modifying agent; a taste modifying agent; a bulking agent or acombination thereof.
 9. The method of claim 1, wherein the dissolutionrate of the granulated Stevia sweetener is at least about 5% greaterthan the dissolution rate of the high solubility Stevia powder.